Melt 1/2 TBSP butter in a flat bottomed pan over medium heat. When butter sizzles, pan is hot enough for the sandwich. Spread the melted butter around the center of the pan with spatula
Rub two slices of bread into the melted butter. Allow first side of each slice to brown, add a 1/2 TBSP butter to the pan, then flip both slices of bread.
Pile the cheese (grated or sliced) on the HOT side of the bread, right up to the edge.
TIP: If using add-ins such as deli meat or fruit, place them in the pan beside the bread slices so they begin to warm.
Cover pan with lid. Let cheese melt until nearly complete, just enough that you can still see some distinct cheese shape (2-3 minutes)
Uncover pan, place add-ins on top of the melted cheese on one piece of bread, then top the sandwich with the second slice of bread.
Using a spatula, flip the entire sandwich over and allow ingredients to meld together for another minute or so.
Transfer sandwich to plate, cut in half and enjoy!